Phenolsulponphthalein Fractional Clearance in Dairy Cattle as a Measure of Renal Function

Open Access
Publisher Website
Google Scholar
Abstract
A new test for renal function in dairy cattle has been devised, based on the rate of clearance of phenolsulfonphthalein (PSP or phenol red) from the blood and body fluids by the kidneys. Two bull calves and two lactating cows were used in these experiments, in which PSP was injected intravenously. The blood plasma level of PSP was determined at various time intervals after the injection. The plasma level of PSP fell rapidly at first and less rapidly thereafter. The over-all curve of plasma levels was differentiated into two first-order regressions in which the logse of PSP concentration were in-versely and rectilinearly related to the time after PSP injection. The first regression was theorized to represent the rate at which PSP moved from the plasma into other body fluids (collectively, its volume of distribution), with a mean slope value in the four animals of 0.171/ minute and a mean biological half-time of 4.4 minutes. The second re-gression was theorized to represent the rate at which PSP was eliminated from its volume of distribution (mean of .36.9% of body weight) by the kidneys and has been termed PSP fractional clearance. It is defined as that fraction of the total volume of distribution of PSP which is cleared of the dye per minute on an instantaneous basis. The mean PSP fractional clearance for the 4 animals was 0.0298, with a mean biological half-time of 24.5 minutes PSP fractional clearance is easily measured and is considered to be a dynamic measure of renal function.